docs(bayn): align runtime contract with paper execution

[gregkonush]

Summary

• document the deployed sandbox PAPER capability instead of the retired OBSERVE-only contract
• distinguish maximum authority from validated durable generation and broker capability composition
• describe research and qualified grants without claiming qualification or economic success

Related Issues

None

Testing

• git diff --check
• verified Bayn README claims against the current application plan, PAPER activation, and execution composition

Breaking Changes

None

Checklist

• Testing section documents the exact validation performed (or N/A with justification).
• Screenshots and Breaking Changes sections are handled appropriately (removed or filled in).
• Documentation, release notes, and follow-ups are updated or tracked.

[chatgpt-codex-connector]

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